The new emission limits regulations have forced engine manufacturers to upgrade the technologies they use and introduce systems that reduce pollutant emissions. One of the parameters that has been worked on to achieve this result is the increased efficiency of the entire power train system, i.e. “FE - Fuel Economy” since, the less fuel is burned, the lower the exhaust emissions.
Of course, the lubricant has evolved to meet the new performance requirements and the upgrades have involved both the chemical composition of the lubricant and its physical characteristics and viscosity. Engine lubrication is mostly hydrodynamic, so the lubricant has a high viscosity; this ensures greater surface protection, but on the other hand results in a loss of power due to the internal friction of the lubricant's molecules. It is therefore necessary to optimise the viscosity of the oil to ensure proper performance.
Engine oil is subjected to high temperatures and high surface sliding speeds. Both of these conditions heavily affect the viscosity of the oil and it is not possible to rely solely on the viscosity class (e.g. SAE 5W-30 or SAE 10W-40). It is therefore necessary to have a measuring system that is able to simulate the real operating conditions in the best way possible. This includes the HT-HS (High Temperature- High Shear) parameter, which is measured using a specific internationally-standardised instrument, in accordance with Standard ASTM D4683.
Is the engine designed for low or very low viscosity fluids? If the answer is NO, choose products with standard viscosity otherwise the bushings may be damaged. If the answer is YES, choose Fuel Economy or Ultra Fuel Economy products based on the recommended specifications.
It is very important to point out that engines that require high HT-HS values may experience early wear and breakage if Fuel Economy oils are used, as a sufficient protective lubricating film is not guaranteed. Conversely, engines that require low HT-HS oils can also run with high HT-HS oils. It is always advisable to check the specifications in the vehicle's use and maintenance manual.